This computerized calculation assumes that the current barometric pressure is 760 mm Hg and that the patient is close to sea level.
Modify the FiO₂if the patient is not on room air. There is no satisfactory method for accurately estimating the FiO₂ for patients managed with nasal canulas.
The formula for doing this calculation by hand is (Calculated O₂ - Measured O₂) or (PAO₂ - PaO₂)
The PAO₂may be calculated with the following formula:
PAO₂ = FiO₂ × (760-47) - (PaCO₂ /0.8)
Return to calculations home page
Return to Emergency Medicine Home Page